A number of techniques have been developed to treat wastewater streams in which contaminants are precipitated and separated from the wastewater stream. Such techniques typically include the addition of a chemical composition, such as ferric or ferrous salts, including ferric sulphate, ferric chloride, ferrous chloride and ferrous sulphate.
In the past few years, there has been increased interest by the water treatment industry in the use of ferrate salts, e.g., as possible substitutes for chlorination processes. For example, potassium ferrate may be used in the treatment and purification of water (see Murmann et al, "Experiments Utilizing FeO.sub.4.sup.-2 for Purifying Water". Water Research, Vol. 8, pp. 79-93 (1974); Gilbert et al., "An Investigation of the Applicability of Ferrate Ion for Disinfection", J. Am. Water Works, Vol. 68(9), pp. 495-497 (1986); and Waite et al., "Iron (VI) Ferrate as a General Oxidant for Water and Wastewater Treatment", Ozone/Chlorine Dioxide Oxid. Prod., Org. Matter Process Conference, (1976), published 1978, pp. 410-425). Ferrate salts are also known as useful for precipitation and/or coagulation of solids in the wastewater.
U.S. Pat. No. 4,983,306 by Deininger et al. and assigned to the University of California, issued Jan. 8, 1991 discloses the use of an alkali metal or alkaline earth metal ferrate to precipitate transuranic elements from wastewater. It is disclosed that a water soluble salt and, in particular, a zirconium salt, can be added with the alkali metal or alkaline earth metal ferrate to provide greater precipitation efficiencies. Specific examples of zirconium salts include those having zirconyl ions (ZrO.sup.2+) and, in particular, zirconium oxychloride (ZrOCl.sub.2 .multidot.8H.sub.2 O), zirconium oxybromide and zirconium oxyiodide.
U.S. Pat. No. 2,873,169 by Seaborg et al. and assigned to the U.S. Atomic Energy Commission, issued Feb. 10, 1959 is directed to the precipitation of plutonium from a first aqueous solution using a first carrier precipitate of a basic peroxidic uranium compound. The carrier and its associated plutonium are then dissolved to form a second aqueous solution, and plutonium is separated from the second solution by means of a second carrier which carries plutonium, leaving in solution the uranium and fission products not previously eliminated. Suitable second carriers are phosphates such as bismuth and zirconium phosphates, rare earth fluorides, particularly lanthanum and cerous fluoride and rare earth oxalates.
U.S. Pat. No. 4,097,430 by Phillips assigned to Magnesium Elektron Limited, issued Jun. 27, 1978 discloses methods for employing ammonium or potassium zirconium carbonates to impart thixotropic properties to aqueous dispersions of polymers and copolymers containing a water soluble organic colloid containing a hydroxy group. U.S. Pat. No. 4,061,720 by Phillips assigned to Magnesium Elektron Limited, issued Dec. 6, 1977 discloses an ammonium or potassium zirconium carbonate solution and a method for making such a solution. The solution is stable for at least 10 hours at a temperature of at least 60.degree. C. The solution is prepared by reacting zirconium basic carbonate with an aqueous solution or slurry of either ammonium or potassium carbonate. The solution can be employed in the method disclosed in U.S. Pat. No. 4,097,430, discussed above.
An article entitled "Atomic Absorption Spectrophotometric Determination of Chromium, Iron and Manganese in Sea Water by the Zirconium Hydroxide Co-Precipitation Method" by Eiko Singuvara, in Hiroshima-Ken Kankyo Senta Kenkyu Hokuku, pages 6-9, 1980, discloses a method for determining trace amounts of Cr, Fe, and Mn cations coprecipitated with zirconium hydroxide.
One problem with certain precipitation agents is that they are ineffective when employed on some contaminant matrices. As used herein, the terms "matrix" and "matrices" mean the combination of soluble and insoluble materials present and encountered in a wastewater stream which can influence a precipitation process designed to remove contaminants from the wastewater stream. A particular problem is encountered with matrices having low suspended solids content and low concentrations of reducing chemicals.
Therefore, it would be advantageous to provide a method and composition for effectively precipitating contaminants from wastewater streams. It would also be advantageous to provide a composition and method for precipitating contaminants from wastewater streams having low suspended solids matrices with low concentrations of reducing chemicals. Furthermore, it would be advantageous if the composition employed for precipitating contaminants was made up of relatively readily available materials. Further, it would be advantageous if the composition was made up of environmentally acceptable chemicals.